1. Field of Invention
The present invention relates to a telescopic device for supporting goods in a container and, more particularly, to a method for making a tube of such a telescopic device.
2. Related Prior Art
Referring to FIG. 1, a conventional telescopic device 13 is used to support goods 11 within a container 10 carried on a tractor 12. Two opposite ends of the telescopic device 13 are firmly abutted against two opposite walls of the container 10. The telescopic device 13 is located against the goods 11. Thus, the goods 11 are kept in position while the tractor 12 is driven on the road.
Referring to FIG. 2, the conventional telescopic device 13 includes an internal tube 21 and an external tube 22. A pad is attached to an end of the internal tube 21. Another pad is attached to an end of the external tube 22. Another end of the internal tube 21 is inserted in another end of the external tube 22. Recessed portions 23 are defined in an external side of the internal tube 21 to receive teeth 31 of a toothed wheel of a maneuvering unit 30 provided on the external tube 22. Thus, an effective length of the conventional telescopic device 13 is retained at a desired value while the pads are abutted against two opposite walls of a container for example. Hence, the telescopic device 13 can position the goods 11. More details of the conventional telescopic device 13 can be found in Taiwanese Utility Mold M293988 issued to the applicant of the present application.
More conventional telescopic devices can be found in Taiwanese Invention Patent Nos. 553332, 560588, 568202 and Taiwanese Utility Models M274466 and M358697. Problems are however encountered during the use of the conventional telescopic devices.
The recessed portions in the internal tube of the conventional telescopic device disclosed in Taiwanese Utility Model M293988 or some others of the conventional telescopic devices are cavities. Referring to FIG. 3, the depth of the recessed portions 23 might be too shallow to hold the teeth 31 firmly. The teeth 31 might be removed from the recessed portions 23 due to vibration during the driving of the tractor 12. In such as case, the effective length of the conventional telescopic device 13 would be reduced. Hence, the pads would not be abutted against the walls of the container 12. Hence, the conventional telescopic device 13 would be dropped from the walls of the container 12, thus failing to support the goods 11.
It is however difficult to make deep cavities in the internal tube 21 by one-step punching without breaking the internal tube 21. This is partly due to a large force for such one-step punching and limited thickness of the internal tube 21.
In the other conventional telescopic devices, apertures are made in the internal tube. The apertures are located close to one another and made through the entire thickness of the internal tube. The strength of the internal tube is inevitably jeopardized.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.